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Feed provided by Physical Chemistry Research. Click to visit.Influence of Surface Heterogeneities on Complexation of Ethylene with Active Sites of NiMCM-41 ...http://www.physchemres.org/article_82179_9665.html
Consecutive adsorption of ethylene molecules on different nanoclusters as representatives of the active sites of NiMCM-41 catalyst was investigated with respect to structural, topological, and energetic properties at the B3LYP/6-311+G* and M06/Def2-TZVP levels of theory. The dimeric adsorption of the ethylene molecules was found to be exothermic on all sites (adsorption enthalpies ranging from &ndash;54.7 to &ndash;13.1 kcal/mol at M06/Def2-TZVP) with the most favorable adsorption on 2T while being non-spontaneous on 5T sites. The &pi; complexation led to positive total charges on the adsorptive molecules, a lengthening of the Ni&ndash;O and C=C distances, and reduced O&ndash;Ni&ndash;O angles, with the smallest changes on 2T and the largest alterations on 4T and 5T. The QTAIM analysis revealed closed-shell interactions between the nickel ion and the olefinic bond. The calculated HOMO&ndash;LUMO gaps attributed the highest and lowest reactivities to the adsorption complexes formed on 2T and 5T (4.22 and 3.11 eV at B3LYP/6-311+G*), respectively. The presented results underscored the importance of a systematic study of the adsorption steps on different active sites of transition metal catalysts.Fri, 31 May 2019 19:30:00 +0100Structural Investigation, Proton and Electron Affinities, Gas Phase Basicities, and Ionization ...http://www.physchemres.org/article_82363_9665.html
Captopril is one of the most significant angiotensin-converting enzyme inhibitors. In spite of numerous experimental and computational studies on its properties, not enough geometrical and thermodynamic data is available on this compound. So, this study aimed to investigate the structural properties and assignment of possible conformers of captopril in the gas-phase. To this end, 1152 unique trial structures were generated by allowing for all the combinations of internal single-bond rotamers and pyrrolidine ring-inversion. A total of 119 conformers were found at the B3LYP/6-311++G** level after three sequential steps of optimization and their relative energies, dipole moments, and rotational constants were obtained. The ionization energies, electron affinities, topical proton affinities, and gas-phase basicities of the first six low-energy conformers of captopril were also calculated via the abovementioned method. As we know, it is widely known that protonation is of great importance in the formation of new structures. Hence, the protonated forms of the favorable captopril conformers were structurally examined.Fri, 31 May 2019 19:30:00 +0100Theoretical Calculations of Refractive Index of Synthesized One and Two Substituted Derivatives ...http://www.physchemres.org/article_82732_9665.html
In order to study the variation of electronic properties, a set of bithiophene derivatives has been &lrm;developed. Here, the effect of substitution on the aromaticity properties of some cyclic &lrm;bithiophene derivative compounds was investigated using theoretical calculations. Calculations &lrm;were performed at B3LYP/6-31+G (d,p) level; and calculated properties included energy, dipole &lrm;moment, total charge on sulfur atom, energy gap, hardness and dipole polarizability. &lrm;Experimental polarizability values were comparable with the theoretical values. Theoretical &lrm;refractive indices were obtained using average polarizability in Lorentz-Lorentz equation. The &lrm;results of comparison between theoretical and experimental refractive indices demonstrated that &lrm;the scaling factors for refractive index and polarizability were 0.99-1.14 and 0.98-1.28, &lrm;respectively. &lrm;Fri, 31 May 2019 19:30:00 +0100Semi Empirical Calculation of Intermolecular Potentials and Transport Properties of Some Binary ...http://www.physchemres.org/article_82743_9665.html
In this study the intermolecular potential energies of some environment-friendly industrial HFC refrigerants were obtained through the inversion method which is based on the corresponding states principle. These potentials were later employed in calculation of transport properties (viscosity, diffusion, thermal conductivity and thermal diffusion factor) of some binary and ternary refrigerant mixtures, in the low density region. Predicted transport properties were compared with the available literature data and gave rise to the acceptable agreement. On the other hand, the interaction potential was fitted to an analytical form, and the calculated low density transport properties were also fitted to the fairly exact equations. In the case of R410A and R421B mixtures, high density viscosity values were also calculated through the Vesovic-Wakeham method. Due to lack of experimental values on high density viscosities of these two mixtures, we could only compare calculated high density viscosities for other available molar compositions of R124-R134a and R125-R32 binary mixtures, with literature data, while again acceptable accordance was observed.Fri, 31 May 2019 19:30:00 +0100